We propose to expand our research efforts in transplantation immunology to a study of host response to tumor oncogenesis. Specifically, we wish to have detailed understanding why immunosurveillance fails and tumors can grow progressively while normal grafts are rejected without immunosuppression. Possible factors investigated will include immunodepression induced by genetic, environmental or tumor-associated factors, antigenic and functional variability of the neoplastic cells within a population, development of immunoresistance in a subpopulation of cells, and role and mechanism of immunologic enhancement. In this latter area, we will test the premise that antibodies to receptor sites located on T-lymphocytes suppress cytotoxic cells primed to kill their target. These are presumed to be antibodies to idiotypic antibodies. Much of the proposed investigation requires purification of membrane antigens, conveniently classified as tumor specific, embryonal, tissue and viral-associated, as well as putative T- and B-lymphocyte receptors for antigen. Advantage will be taken of the heterologous or homologous antisera to these antigens prepared for investigation to make a screening panel of radioimmune assays for a series of human neoplasms to test the feasibility and advantages of earlier detection of neoplasms. Similarly, we will test the usefulness of fluorescein- conjugated anti-tumor antisera in the histologic diagnosis of malignancy on biopsied tumor.